Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$41.91	3.713%	$43.4661	$43.47	$43.45	$43.50
Purchase #2	$134.90	5.626%	$142.4895	$142.49	$142.50	$142.50
Purchase #3	$88.68	12.332%	$99.616	$99.62	$99.60	$99.60
Purchase #4	$43.91	9.557%	$48.1065	$48.11	$48.10	$48.10
Purchase #5	$15.49	11.282%	$17.2376	$17.24	$17.25	$17.20
Purchase #6	$196.51	6.172%	$208.6386	$208.64	$208.65	$208.60
Purchase #7	$5.64	5.833%	$5.969	$5.97	$5.95	$6.00
7 purchase totals =	$527.04		$565.5233	$565.54	$565.50	$565.50